var rotateLeft = function (matrix) {
  var rows = matrix.length;
  var columns = matrix[0].length;
  var res = [];
  for (var row = 0; row < rows; ++row) {
      res.push([]);
      for (var column = 0; column < columns; ++column) {
          res[row][column] = matrix[column][columns - row - 1];
      }
  }
  return res;
};

var Tile = function (value, row, column) {
  this.value = value || 0;
  this.row = row || -1;

  this.column = column || -1;
  this.oldRow = -1;
  this.oldColumn = -1;
  this.markForDeletion = false;
  this.mergedInto = null;
  this.id = Tile.id++;
};

Tile.id = 0;

Tile.prototype.moveTo = function (row, column) {
  this.oldRow = this.row;
  this.oldColumn = this.column;
  this.row = row;
  this.column = column;
};

Tile.prototype.isNew = function () {
  return this.oldRow === -1 && !this.mergedInto;
};

Tile.prototype.hasMoved = function () {
  return (this.fromRow() !== -1 && (this.fromRow() !== this.toRow() || this.fromColumn() !== this.toColumn())) ||
      this.mergedInto;
};

Tile.prototype.fromRow = function () {
  return this.mergedInto ? this.row : this.oldRow;
};

Tile.prototype.fromColumn = function () {
  return this.mergedInto ? this.column : this.oldColumn;
};

Tile.prototype.toRow = function () {
  return this.mergedInto ? this.mergedInto.row : this.row;
};

Tile.prototype.toColumn = function () {
  return this.mergedInto ? this.mergedInto.column : this.column;
};

var Board = function () {
  this.tiles = [];
  this.cells = [];
  for (var i = 0; i < Board.size; ++i) {
      this.cells[i] = [this.addTile(), this.addTile(), this.addTile(), this.addTile()];
  }
  this.addRandomTile();
  this.setPositions();
  this.won = false;
};

Board.prototype.addTile = function () {
  var res = new Tile();
  Tile.apply(res, arguments);
  this.tiles.push(res);
  return res;
};

Board.size = 4;

Board.prototype.moveLeft = function () {
  var hasChanged = false;
  for (var row = 0; row < Board.size; ++row) {
      var currentRow = this.cells[row].filter(function (tile) {
          return tile.value !== 0;
      });
      var resultRow = [];
      for (var target = 0; target < Board.size; ++target) {
          var targetTile = currentRow.length ? currentRow.shift() : this.addTile();
          if (currentRow.length > 0 && currentRow[0].value === targetTile.value) {
              var tile1 = targetTile;
              targetTile = this.addTile(targetTile.value);
              tile1.mergedInto = targetTile;
              var tile2 = currentRow.shift();
              tile2.mergedInto = targetTile;
              targetTile.value += tile2.value;
          }
          resultRow[target] = targetTile;
          this.won = this.won || (targetTile.value === 2048);
          hasChanged = hasChanged || (targetTile.value !== this.cells[row][target].value);
      }
      this.cells[row] = resultRow;
  }
  return hasChanged;
};

Board.prototype.setPositions = function () {
  this.cells.forEach(function (row, rowIndex) {
      row.forEach(function (tile, columnIndex) {
          tile.oldRow = tile.row;
          tile.oldColumn = tile.column;
          tile.row = rowIndex;
          tile.column = columnIndex;
          tile.markForDeletion = false;
      });
  });
};

Board.fourProbability = 0.1;

Board.prototype.addRandomTile = function () {
  var emptyCells = [];
  for (var r = 0; r < Board.size; ++r) {
      for (var c = 0; c < Board.size; ++c) {
          if (this.cells[r][c].value === 0) {
              emptyCells.push({r: r, c: c});
          }
      }
  }
  var index = Math.floor(Math.random() * emptyCells.length);
  var cell = emptyCells[index];
  var newValue = Math.random() < Board.fourProbability ? 4 : 2;
  this.cells[cell.r][cell.c] = this.addTile(newValue);
};

Board.prototype.move = function (direction) {
  // 0 -> left, 1 -> up, 2 -> right, 3 -> down
  this.clearOldTiles();
  for (var i = 0; i < direction; ++i) {
      this.cells = rotateLeft(this.cells);
  }
  var hasChanged = this.moveLeft();
  for (var i = direction; i < 4; ++i) {
      this.cells = rotateLeft(this.cells);
  }
  if (hasChanged) {
      this.addRandomTile();
  }
  this.setPositions();
  return this;
};

Board.prototype.clearOldTiles = function () {
  this.tiles = this.tiles.filter(function (tile) {
      return tile.markForDeletion === false;
  });
  this.tiles.forEach(function (tile) {
      tile.markForDeletion = true;
  });
};

Board.prototype.hasWon = function () {
  return this.won;
};

Board.deltaX = [-1, 0, 1, 0];
Board.deltaY = [0, -1, 0, 1];

Board.prototype.hasLost = function () {
  var canMove = false;
  for (var row = 0; row < Board.size; ++row) {
      for (var column = 0; column < Board.size; ++column) {
          canMove = canMove || (this.cells[row][column].value === 0);
          for (var dir = 0; dir < 4; ++dir) {
              var newRow = row + Board.deltaX[dir];
              var newColumn = column + Board.deltaY[dir];
              if (newRow < 0 || newRow >= Board.size || newColumn < 0 || newColumn >= Board.size) {
                  continue;
              }
              canMove = canMove || (this.cells[row][column].value === this.cells[newRow][newColumn].value);
          }
      }
  }
  return !canMove;
};

module.exports = Board;
